Had same issue for a while as well, kept clicking on 2017 but it kept telling me my file was in a higher version, open 2016 etc etc. when I had just upgraded.

you have done all the right things, clear cookies etc. what I did after that was go to control panel and logoff remote sessions manually, close out of browser, open browser, login screen, login and click 2017, hopefully this will work for you as well.